Make URIs absolute when encoding NT.

src/codec/codec_nt.c

@@ -2,9 +2,10 @@
 
 
 /// NT codec iterator type.
-typedef struct {
+typedef struct nt_codec_iterator {
     const VOLK_Codec *  codec;      // Codec that generated this iterator.
     VOLK_GraphIterator *gr_it;      // Graph iterator.
+    const VOLK_Term *   gr_uri;     // Graph URI.
     size_t              cur;        // Internal cursor.
     VOLK_rc             rc;         // Internal return code.
     char *              str_s,      // Temporary string.
@@ -115,6 +116,7 @@ gr_to_nt_init (const VOLK_Graph *gr)
 
     it->codec = &nt_codec;
     it->gr_it = VOLK_graph_lookup(gr, NULL, NULL, NULL, &it->cur);
+    it->gr_uri = VOLK_graph_uri (gr);
 
     return it;
 }
@@ -124,12 +126,25 @@ static VOLK_rc
 gr_to_nt_iter (void *h, char **res) {
     VOLK_NTCodecIterator *it = h;
     VOLK_Triple *spo = NULL;
+
     VOLK_rc rc = VOLK_graph_iter_next (it->gr_it, &spo);
     if (rc != VOLK_OK) goto finally;
 
-    term_to_nt (spo->s, &it->str_s);
+    // If IRIRefs are relative to the graph URI, make them absolute.
+    VOLK_Term *abs_s, *abs_o;
+    if (spo->s->type == VOLK_TERM_IRIREF)
+        abs_s = VOLK_iriref_new_abs (it->gr_uri, spo->s);
+    else abs_s = spo->s;
+    if (spo->o->type == VOLK_TERM_IRIREF)
+        abs_o = VOLK_iriref_new_abs (it->gr_uri, spo->o);
+    else abs_o = spo->o;
+
+    term_to_nt (abs_s, &it->str_s);
     term_to_nt (spo->p, &it->str_p);
-    term_to_nt (spo->o, &it->str_o);
+    term_to_nt (abs_o, &it->str_o);
+
+    if (abs_s != spo->s) VOLK_term_free (abs_s);
+    if (abs_o != spo->o) VOLK_term_free (abs_o);
     VOLK_triple_free (spo);
 
     // 3 term separators + dot + newline + terminal = 6